With the evolution of battery technology, many electronic devices are usually configured with a battery therein. The energy required for the operation of the electronic device can be provided by the electrical quantity stored in the battery. The electrical quantity stored in the battery will gradually decrease with the operation of the electronic device. In order to prevent that the electrical quantity of the electronic device is completely depleted and the operation of the electronic device is stopped without warning, many electronic devices are having a function of estimating the remaining capacity of the battery of itself. By the estimation of the remaining capacity of the battery, the user of the electronic device can perform charging on the battery when the electrical quantity of the battery is insufficient.
The method of the look-up table, for example, OVC lookup table, is often adopted for estimating the remaining capacity of the battery. The battery has a characteristic that a specific voltage will correspond to a specific capacity. The OVC lookup table lists each of battery capacities that is corresponding to each of voltages. A corresponding capacity of battery can be found from the voltage look-up table based on the detection of the current battery voltage. Although the OVC look-up table method can estimate the battery capacity quickly and simply, the voltage of the battery in use is easy to flutter, for example, the voltage will drop suddenly and then rise back slowly when the battery just starts to discharge, or the voltage will rise suddenly and then drop back slowly when the battery just starts to charge. Accordingly, the battery voltage generates a sharp change at a specific time based on the charge or discharge of the battery, so that the battery capacity estimated by the OVC look-up table method will be inaccurate. Furthermore, the battery will gradually generate physical aging with the use of time, such that the storage capability of the battery is getting worse; but, the OVC look-up table method is unable to forecast the aging of battery, resulting in the estimation of battery capacity that is more inaccurate.